Four mineral constituents: C.sub.3 S (tricalcium silicate), C.sub.2 S (dicalcium silicate), C.sub.3 A (tricalcium aluminate) and C.sub.4 AF (tetracalcium alumina ferrite), constitute the major part of cement. Their relative amounts and form of crystallization govern such properties as strength and durability. For instance, at room temperaure, C.sub.2 S is thermodynamically stable in the .gamma.-form; yet this form is not desirable in cement since it hydrates into tobermorites (which gives strength to cement) only with difficulty.
A study of powder diagrams of the .alpha.'-, .alpha.-, .beta.- and .gamma.-forms of C.sub.2 S reveals that fineness of particle size is critical to stability. The .alpha.'-phase is always transformed during cooling into the .beta.-phase. When .beta. grains are smaller than a particular critical size [in the order of (5.mu.).sup.3 ], the probability that such grains contain a .gamma. nucleus is very slight; thus, metastable .beta. phase can be preserved at ordinary temperatures. On the other hand, when grains are large [e.g. (30.mu.).sup.3 ], a .gamma. nucleus is always present. Such nucleus grows until all of the .beta. phase is turned into non-reactive .gamma. phase, which yields only a weak cement.
Criticality of particle size and quenching is discussed in "CHEMISTRY OF CEMENT Proceeding of the Fourth International Symposium, Washington, 1960", Monograph 43, Volume 1, pages 21 and 389, U.S. Department of Commerce, National Bureau of Standards.
Means and methods for preparing "mineral wools" (e.g., mineral, rock and glass whole) are well known. These wools differ greatly from the present fibers, however. Mineral, rock and glass wools are amorphous, super-cooled liquids and generally devoid of crystals. U.S. Pat. No. 3,360,593 (Rau et al.) teaches that mineral wools containing "property-destroying" crystal nuclei are undesirable. Rau's invention relates to a process for avoiding crystal formation in blown material fibers. U.S. Pat. No. 2,051,279 (Thorndyke) relates to the preparation of "flexible and highly resilient" glass and mineral fibers; no teaching of fibers containing .beta.-phase crystals of C.sub.2 S is found, U.S. Pat. No. 3,985,935 (Brodmann) also relates to the production of vitreous fibers. Although "mineral wools" are useful cement components, they alone cannot be hydrated to form cement; activators (e.g. lime) must first be added.
Quenching with high-pressure steam or air streams is common in the mineral wool industry. J. R. Thoenen (Mineral Wool, Bureau of Mines Information Circular No. 6984R, 1939) reported on twenty-five mineral wool plants, a majority of which employed steam to quench a molten slag stream. Because the present process produces cement, steam or even normal air cannot be used as these cause premature hydration and thus yield a useless product.
Prior attempts to manufacture cement in blast and rockwool furnaces have not been successful. The highly basic molten slag causes refractory linings to melt away as the linings react with excess calcium in the slag. Rockwool furnaces produce fibers which are too large and thus contain C.sub.2 S wholly in unreactive .gamma. form. Further, the resulting product is prematurely hydrated even at the extremely low reactive humidity of the furnace.